1. Field of the Invention
The invention is based on an apparatus for controlling gas exchange valves in combustion cylinders of an internal combustion engine.
2. Description of the Prior Art
In a known apparatus of the type with which this invention is concerned. (German Patent Disclosure DE 198 26 047 A1), each valve actuator, whose adjusting piston is connected integrally to the valve tappet of the associated gas exchange valve, communicates constantly by its first work chamber with a high-pressure source and with its second work chamber on the one hand is connected to a first electrical control valve that in alternation closes or opens a supply line to the high-pressure source and on the other to a second control valve that alternately opens or closes a relief line. The electrical control valves are embodied as 2/2-way magnet valves with spring restoration. When the control valves are without current, the first work chamber is at high pressure as before, while the second work chamber is disconnected from the high-pressure source and is connected to the relief line. The gas exchange valve is closed. For opening the gas exchange valve, both control valves are supplied with current. Because of the switchover of the control valves, the second work chamber of the valve actuator is blocked on the one hand from the relief line by the second control valve and on the other is made to communicate, by the first control valve, with the supply line to the high-pressure source. The gas exchange valve opens; the length of the opening stroke depends of the electrical control signal applied to the first electrical control valve, and the opening speed depends on the pressure fed in from the high-pressure source. To keep the gas exchange valve in a defined open position, the first control valve is then switched to be without current, so that it blocks off the supply line to the second work chamber of the valve actuator. In this way, by means of an electrical control unit for generating control signals, all the valve opening positions of the gas exchange valve can be set. For controlling each gas exchange valve, two electrical control valves are required, which correspondingly subject the associated valve actuator to hydraulic pressure.